Salt of morphine-6-glucuronide

ABSTRACT

Hydrobromide salt of morphine-6-β-D-glucuronide (M6G.HBr), a medicament, and a pharmaceutical composition comprising the M6G.HBr are disclosed. Methods of treating diseases using M6G.HBr, use of M6G.HBr as a medicament, in particular as an analgesic, are provided. Methods of making M6G.HBr and pharmaceutical compositions comprising the M6G.HBr also are provided.

This invention relates to a salt of morphine-6-β-D-glucuronide (M6G; see FIG. 1) with improved stability, and to use of the salt as a medicament, in particular as an analgesic.

M6G is a metabolite of morphine which is known to be a more powerful analgesic than morphine itself and yet has fewer side effects. Methods of preparation of M6G are described in WO 93/03051, WO 93/05057, WO 99/58545 and WO 99/38876.

Whilst M6G base is stable when stored at −20° C., it does degrade when stored at room temperature. This degradation is not only noted by an increase in detectable degradation products, but also by a marked colour change of the compound. This will limit the shelf life of M6G base at ambient temperature.

It has now been found that the hydrobromide salt of M6G (M6G.HBr) is surprisingly stable compared to M6G base and other M6G salts, in particular the hydrochloride (M6G.HCl) and sulphate (M6G₂.H₂SO₄) salts. M6G.HBr showed a very limited amount of degradation and no discolouration after storage at room temperature for six years (see Example 1 below).

According to the invention there is provided a hydrobromide salt of M6G (M6G.HBr). Methods of preparation of M6G.HBr are described in Examples 2 and 3 below.

M6G.HBr may be used as a medicament, in particular as an analgesic. Examples are for the treatment of moderate to severe, acute and chronic nociceptive pain (such as post-operative pain, pain associated with malignant and non-malignant diseases), and neuropathic pain.

M6G.HBr may be administered by any suitable route. Examples are as a solid formulation (e.g. for oral, dry powder inhalation), as a solution formulation (e.g. intravenous (including infusion for PCA), subcutaneous, intranasal, or sublingual), or as a transdermal formulation (e.g. by simple diffusion or by enhanced electrophoretic methods). Transdermal administration of pharmaceutically acceptable acid addition salts of M6G is described in U.S. Pat. No. 5,705,186.

According to the invention there is also provided a pharmaceutical composition comprising an analgesically effective amount of M6G.HBr together with a pharmaceutically acceptable carrier, excipient, or diluent.

An analgesically effective amount of M6G.HBr will vary with the route of administration, and with factors such as the age, sex, weight, and condition of the subject being administered, and with the type of condition being treated. In general, a suitable dose for an acute condition will be lower than for a chronic condition.

A suitable dose is in the range of 1-1000 mg/70 Kg, preferably 1-200 mg/70 Kg, more preferably in the range of 5-75 mg/70 Kg. A preferred dose for acute use is in the range of 5-75 mg/70 Kg. A preferred dose for chronic use is in the range of 30-500 mg/kg. Dosage for routes of administration where bio-availability is high (e.g. intravenous, subcutaneous, intranasal, sublingual) will be lower than for routes with low bio-availability (e.g. oral).

M6G.HBr may also be used for the symptomatic treatment of breathlessness in patients with advanced cancer. Any suitable route of administration may be used, but a preferred route is inhalation of nebulized M6G.HBr. The effect of administration of nebulized M6G is described by Quigley et al (in J. Pain Symptom Manage., Letters, Vol 23, No. 1 (2002), pages 7-9). A dosage of M6G.HBr effective for the treatment of breathlessness in a subject with advanced cancer will vary with the route of administration, and with factors such as the age, sex, weight, and condition of the subject being administered. A suitable dose is in the range of 1-200 mg/70 Kg, preferably in the range of 5-75 mg/70 Kg.

There is further provided according to the invention a method of making M6G.HBr which comprises: (i) contacting a hydrogen bromide solution with a solution of M6G in methanol; (ii) contacting the solution resulting from step (i) with an organic solvent to precipitate M6G.HBr; and (iii) isolating M6G.HBr precipitated in step (ii).

Preferably the solutions and solvent are at −15° C., or below. This minimises formation of degradation products.

Preferably the precipitated M6G.HBr is washed to minimise the amount of organic solvent present. For example, the precipitated M6G.HBr may be washed with diethyl ether.

A preferred organic solvent is 2-propanol.

According to a preferred method a cooled diluted solution of HBr is added to a continuously stirred, cooled (to at least −15° C.) solution of M6G in methanol. Then 2-propanol (or other suitable organic solvent) is added, and the resulting suspension is maintained below −15° C., while continuously stirring. Following stirring of the suspension the resultant crystals are filtered and washed with a suitable solvent (e.g. 2-propanol or diethyl ether) and dried by suitable means (e.g. under vacuum at room temperature).

The following examples 1 and 2 relate to the stability of M6G salts at room temperature, and methods of preparation of M6G salts, respectively. Table 1 shows the stability data for the M6G salts tested, and FIG. 1 shows the chemical structure of M6G and identified degradants. Example 3 relates to the stability of M6G salts and base at 25° C./60% RH, 40° C./75% RH and 60° C. Tables 2-4 show the data relating to example 3.

EXAMPLE 1 Stability of M6G Salts at Room Temperature over 6 Years

Analytical Investigation by HPLC:

Samples of the hydrochloride salt (M6G.HCl) (205-2056), the sulphate salt (M6G₂.H₂SO₄) (205-2060), and the hydrobromide salt (M6G.HBr) (205-2059) of M6G were stored at room temperature for almost 6 years and then analysed by HPLC. The results are shown in Table 1, together with the results of HPLC analysis of samples prepared under similar conditions a few months earlier.

Results:

M6G.HCl (205-2056): The content of M6G decreased to 69% (starting from ˜82%). HN-67002 and HN-67003 (which are typically oxidation products) increased to 1.3% and 2.1% respectively. The content of HN-33177, a synthetic impurity of M6G, remained unchanged. However, there are 17 peaks present in the chromatogram that cannot be identified by retention time. The total of these impurities is 9.2 area %.

M6G₂.H₂SO₄ (205-2060): The content of M6G decreased to 63% (starting from −77%). HN-67002 and HN-67003 increased to 1.1% and 1.8% respectively. The content of HN-33177 did not change. However, there are 13 peaks present in the chromatogram that cannot be identified by retention time. The total of these impurities is 10.7 area % with a dominant peak at 23.5 min (6.55 area %).

M6G.HBr (205-2059): The content of M6G did not decrease at all and the content of HN-67002 (0.5%) and HN-67003 (0.2%) is much lower than in the samples discussed above. There are only 4 additional peaks present in the chromatogram. None of these are bigger than 0.4 area %. The result is superior to the two other salts tested.

Conclusion:

The hydrobromide salt of M6G shows very limited degradation and was not discoloured after storage for six years at room temperature compared to the free base and other salts investigated. Thus, the hydrobromide salt of M6G has improved stability at room temperature compared to the hydrochloride and sulphate salts of M6G.

EXAMPLE 2 Preparation of Hydrobromide and Sulphate Salts of M6G

Preparation of Q 3196 (M6G.HBr, 304-4428):

4.99 g of M6G.2H₂O were dissolved in 11 ml of Methanol and cooled to −15° C. 1.16 ml of HBr (48% in water) was diluted with 0.85 ml of Methanol and cooled to −15° C. and added slowly to the solution of M6G. A clear, highly viscous, pale yellow solution was obtained. The solution was stirred for 5 minutes before 100 ml 2-propanol (−15° C.) were added. The product precipitated immediately. The slurry was stirred for 3.5 hours at −20° C., the crystals were filtered off, washed with 37.5 ml cold 2-propanol (−20° C.) and dried at room temperature in a high vacuum. The yield was 5.61 g.

Preparation of Q 3195 (M6G₂.H₂SO₄, 304-4429):

5.02 g of M6G.2H₂O were dissolved in 11 ml of Methanol and cooled to −15° C. 0.35 ml of H₂SO₄ (96%) was diluted with 0.85 ml of Methanol and cooled to −15° C. and added slowly to the solution of M6G. A clear, highly viscous, pale yellow solution was obtained. The solution was stirred for 5 minutes before 100 ml 2-propanol (−15° C.) were added. The product precipitated immediately. The slurry was stirred for 3.5 hours at −20° C., the crystals were filtered off, washed with 37.5 ml cold 2-propanol (−20° C.) and dried at room temperature in a high vacuum. The yield was 5.36 g.

EXAMPLE 3 Stability of M6G Salts after 1 Month at 60° C. and 3 Months at 25° C./60% Relative Humidity and 40° C./75% Relative Humidity

The analytical data below gives clear evidence that the stability of the hydrobromide salt is superior to all other salts assessed and in addition would appear to be more stable than Morphine-6-glucuronide base. The data demonstrates that the hydrobromide salt is stable when subjected to storage conditions of 25° C./60% RH and 40° C./75% RH for 3 months and 60° C. for 1 month. The base appears to be relatively stable to storage conditions of 25° C./60% RH after three months, but shows signs of degradation at 40° C./75% RH over 3 months and 60° C. over 1 month.

All of the other salts show some form of degradation at 25° C./60% RH and at elevated temperature and humidity.

The Morphine-6-glucuronide sulphate salt is the least stable at 25° C./60% RH, whilst the Morphine-6-glucuronide hydrochloride is the least stable at 40° C./75% RH as this shows the greatest level of degradation of all the salts.

Introduction

Various salts and the base of Morphine-6-glucuronide have been subjected to storage conditions of 25° C./60% RH and 40° C./75% RH for 3 months and 60° C. for 1 month.

The analytical testing comprised of:

Visual appearance

Water content (% w/w) by Karl Fisher analysis

Assay (% w/w) and related substances determination

Colour of solution by UV spectrophotometry.

The results obtained for each test were used to assess the stability of the various salts and the base.

Experimental procedures

Materials

Test Item Characterization, Sample Description

Six different salts of morphine-6-glucuronide were prepared from morphine-6-glucuronide base; the hydrobromide (HBr), sulphate (H₂SO₄), phosphate (H₃PO₄), hydrochloride (HCl), fumarate and maleate. The HBr salt was prepared by the method described in Example 2. The only difference was that after the 2-propanol slurry was filtered, the solid was then washed three times with diethyl ether, before drying under vacuum at room temperature. This additional step was employed to remove as much 2-propanol from the salt as possible.

The other inorganic salts (sulphate, phosphate, hydrochloride) were prepared in a similar way, i.e. by addition of the relevant acid to a cooled stirring suspension of morphine-6-glucuronide base in methanol, trituration of the resultant solution with cooled 2-propanol to form a suspension, and then continuous stirring at low temperature. Filtration of the solid is followed by washing with diethyl ether, and then drying at room temperature under reduced pressure.

The maleate and fumarate were prepared by the addition of the desired acid, on stirring at room temperature, to an aqueous solution of morphine-6-glucuronide base until all material was dissolved. The solution was then freeze dried to produce the required solid.

The same batch of morphine-6-glucuronide base (Batch M01003) was used to prepare each salt. This batch had been synthesised and tested to confirm identity, chemical and microbiological purity.

All salts prepared were tested to confirm appearance, assay (% w/w) by HPLC, confirmation of presence of correct counter ion, water content (% w/w) by Karl Fisher analysis, residual solvent analysis by GC and determination of colour of solution by measurement of UV absorbance of a 5% w/v solution at 420 nm.

Description of Salts of Morphine-6-glucuronide: Molecular Batch Description Weight Number M6G Hydrobromide salt 542.37 JCCA24B M6G.HBr M6G Sulphate salt 1021.00 JCCA25B (M6G)₂.H₂SO₄ M6G Phosphate salt 559.46 JCCA26B M6G.H₃PO₄ M6G Fumarate salt 1039.00 MM13A (M6G)₂ Fumarate M6G Maleate salt 1039.00 MM14A (M6G)₂ Maleate M6G Hydrochloride salt 497.92 MM10C M6G.HCl

Description of Reference Substances Used in Testing of Salts: Batch Reference substance Description number HN-33169 M6G 401-2055 HN-33177 Synthetic 401-2052 impurity HN-75083 Degradant 401-2054 HN-75076 Degradant 401-2044 HN-67003 Degradant 401-2058 Morphine sulphate Degradant 40IK1192 pentahydrate

Each test material was stored between 2-8*C prior to placing on stability. Each material was sub-divided into 900 mg aliquots, transferred to brown opaque HDPE plastic bottles and flushed with Argon prior to sealing. Sufficient samples were provided for each time point as well as spares for each storage condition. The samples were placed in appropriate incubators previously commissioned at storage conditions 25° C./60% RH, 40° C./75% RH and 60° C.

The reference materials were stored under secure conditions at −20° C. or below until required for testing.

Methods

The samples were stored for analysis according to the following table: Storage Condition Initial 1 month 3 months 25° C./60% RH X X X 40° C./75% RH X X 60° C. X — X = Appearance, Water content by Karl Fischer analysis, Assay and Related Substances and Colour by UV/Vis spectrophotometry. Testing Procedures Test for Identity Content and Impurities

Testing was performed in duplicate (2×25 mg) in accordance with a stability indicating HPLC assay method. The assay results were reported as M6G as is, M6G as the anhydrous, solvent free material and the anhydrous solvent free material corrected for the salt form using the relevant conversion factor.

Water Content by Karl Fisher Analysis

Water content was determined in duplicate on an aliquot of equilibrated material (approximately 100 mg) using a Tritrino 720 KFS Titrator.

Colour by Visible Spectrophotometry

A 5% w/v solution of test material was prepared in water and the absorbance measured at 420 nm in a 1 cm silica cell using a Unicam UV4 Visible/UV spectrophotometer.

Results

These are shown in Tables 2-4.

Discussion

On storage for 3 months at 25° C./60% RH the hydrobromide, hydrochloride, phosphate and base remain as white crystalline solids, the other salts showing varying degrees of colouration. However on storage at 40° C./75% RH over the same period, all the salts (except the hydrobromide) plus the base show signs of becoming yellow in appearance. The change in appearance is reflected in the results for colour of solution, which increases in value as the yellow colour of the solid becomes more intense.

The general trend in moisture content is that the higher the storage humidity the greater the moisture content of the samples. The exception however is the base, where the moisture content is reasonably consistent regardless of storage condition. Of the salts the largest change in moisture content is with the phosphate (increase of around 8% at 40° C./75% RH compared to initial)

Review of the 3 month assay data shows some interesting trends. The most stable materials (based on % w/w assay) are the hydrobromide, base and phosphate. It should be noted that the reason that the phosphate assay values are high throughout the study (around 110%±5%), is that there were some problems in the preparation of this salt. These issues resulted in the material being present as a mixture of phosphate/base in a ratio of approximately 10.8:1. The maleate and fumarate show a drop in assay of around 10% after 3 months at 40° C./75% RH compared to the initial values. Interestingly the hydrochloride shows a small decrease in assay after 3 months storage at 25° C./60% RH (around 6% compared to initial), however a dramatic reduction at 3 months storage at 40° C./75% RH (approx 34% decrease compared to initial). This reduction is in fact more than that seen with the sulphate salt, which from the 1-month data alone was thought to be the most unstable salt. The low assay value seen at 3 months 40° C./75% RH, may be linked to the breakdown of the crystal form at high humidity resulting in a high degree of degradation. This degradation is reflected in the amount of degradation products seen in this sample (total of around 54.5%)

Even after 3 months storage at 40° C./75% RH there is basically no increase in the amount of degradation products in the hydrobromide salt as measured by HPLC. At the same conditions, there is an increase of approximately 3% in the amount of degradation products in the base. The levels of degradation are similar for the fumarate and maleate, slightly less for the phosphate. The least stable salts are the sulphate and the hydrochloride, with some indication that the hydrochloride is more stable than the sulphate at 25° C./60% RH, but the reverse being the case at 40° C./75% RH.

Conclusion

The results obtained indicate that the hydrobromide salt appears more stable than all other salts and the base. An overall review of the data suggests the following order of stability:

Hydrobromide>base>>phosphate/maleate/fumarate>sulphate/hydrochloride TABLE 1 Stability Data of M6G-Salts Stored at Ambient Temperature in Example 1 Unknown related Elasped Assay Assay substances Time M6G M6G HN- HN- HN- HN- HN- (sum area Salt Batch (years) uncorr. corr. 67002 75076 Morphine 75083 67003 33177 %) Hydrochloride 205- 0 82.2 88.7 — n.d. n.d. <0.1 — 0.3 <0.1 2042 205- 6 69.3 74.8 1.3 n.d. 0.2 n.d. 2.1 0.2 9.2 2056 Sulphate 205- 0 77.2 93.6 — n.d. n.d. <0.1 — 0.2 0.2 2041 205- 6 63.3 76.8 1.1 n.d. 0.2 n.d. 1.8 0.3 10.7 2060 Hydrobromide 205- 0 77.2 90.7 — n.d. n.d. <0.1 — 0.3 <0.1 2045 205- 6 81.9 96.3 0.5 n.d. n.d. n.d. 0.2 0.4 1.0 2059 Free base F12061 0 N/A 98.2 n.d. n.d. n.d. n.d. n.d. 0.7 <0.1 F12061 5 N/A 81.2 n.d. n.d. 0.3 n.d. n.d. 0.8 11.8 n.d. not detectable — not investigated M6G uncorr. content calculated as M6G base M6G corr. content calculated as M6G derivative = M6G uncorr. × f f = molecular weight (M6G-derivative)/molecular weight (M6G)

TABLE 2 Appearance, Moisture and Colour by Visible spectrophotometry: Example 3 Laboratory Time Storage Moisture Colour Description Reference Point Condition Appearance (% w/w) (Abs@420 nm) Morphine-6- 299615 Initial White crystalline powder 3.77 0.136 glucuronide 307571 1 month 25° C./60% RH White crystalline powder 4.28 0.244 sulphate 318587 3 months Pale yellow crystalline powder 5.54 0.406 307578 1 month 40° C./75% RH Slightly yellow crystalline powder 5.93 0.430 318594 3 months Slightly yellow crystalline powder 8.31 1.056 307585 1 month 60° C. Pale yellow crystalline powder 4.68 1.714 Morphine-6- 299616 Initial White crystalline powder 2.38 0.029 glucuronide 307570 1 month 25° C./60% RH White crystalline powder 2.56 0.073 hydrobromide 318588 3 months White crystalline powder 3.28 0.046 307577 1 month 40° C./75% RH White crystalline powder 3.19 0.064 318595 3 months White crystalline powder 4.24 0.066 307584 1 month 60° C. White crystalline powder 1.95 0.261 Morphine-6- 299617 Initial White crystalline powder 4.31 0.059 glucuronide 307565 1 month 25° C./60% RH White crystalline powder 5.10 0.147 hydrochloride 318589 3 months White crystalline powder 6.06 0.253 307572 1 month 40° C./75% RH Slightly yellow crystalline powder 6.24 0.444 318596 3 months Yellow crystalline powder 9.02 2.107 307579 1 month 60° C. Pale yellow crystalline powder 4.44 1.183 Morphine-6- 299618 Initial White crystalline powder 6.80 0.016 glucuronide 307569 1 month 25° C./60% RH White crystalline powder 7.26 0.034 fumarate 318590 3 months Pale yellow crystalline powder 8.00 0.141 307576 1 month 40° C./75% RH Pale yellow crystalline powder 7.94 0.264 318597 3 months Yellow crystalline powder 10.89 1.008 307583 1 month 60° C. Yellow crystalline powder 5.98 0.794 Morphine-6- 299619 Initial White crystalline powder 6.14 0.017 glucuronide 307568 1 month 25° C./60% RH White crystalline powder 7.53 0.084 maleate 318591 3 months Pale yellow crystalline powder 7.14 0.209 307575 1 month 40° C./75% RH Pale yellow crystalline powder 7.60 0.297 318598 3 months Yellow crystalline powder 9.24 0.879 307582 1 month 60° C. Yellow crystalline powder 5.01 0.739 Morphine-6- 299620 Initial White crystalline powder 3.12 0.034 glucuronide 307567 1 month 25° C./60% RH White crystalline powder 3.91 0.053 phosphate 318592 3 months White crystalline powder 5.06 0.098 307574 1 month 40° C./75% RH Slightly yellow crystalline powder 9.28 0.308 318599 3 months Slightly yellow crystalline powder 11.88 0.878 307581 1 month 60° C. Pale yellow crystalline powder 5.12 0.787 Morphine-6- 299622 Initial White crystalline powder 9.80 0.017 glucuronide 307566 1 month 25° C./60% RH White crystalline powder 9.00 0.040 base 318593 3 months White crystalline powder 9.53 0.132 307573 1 month 40° C./75% RH Pale yellow crystalline powder 9.68 0.182 318600 3 months Yellow crystalline powder 9.85 0.680 307580 I month 60° C. Yellow crystalline powder 8.21 0.541

TABLE 3 Assay: Example 3 M6G Assay (% w/w) Laboratory Time Storage Corrected for the Description Reference Point Condition As is basis Anhydrous basis salt form Morphine-6- 299615 Initial 80.62 88.49 97.87 glucuronide 307571 1 month 25° C./60% RH 73.58 81.82 90.51 Sulphate 318587 3 months 69.08 77.05 85.24 307578 1 month 40° C./75% RH 65.04 73.67 81.50 318594 3 months 59.39 68.38 75.64 307585 1 month 60° C. 57.15 63.84 70.62 Morphine-6- 299616 Initial 82.26 83.63 98.29 glucuronide 307570 1 month 25° C./60% RH 83.02 85.18 100.11 hydrobromide 318588 3 months 84.30 86.19 101.30 307577 1 month 40° C./75% RH 82.40 85.09 100.01 318595 3 months 83.14 85.85 100.90 307584 1 month 60° C. 82.82 84.44 99.25 Morpbine-6- 299617 Initial 81.63 93.28 100.65 glucuronide 307565 1 month 25° C./60% RH 79.21 92.03 99.30 hydrochloride 318588 3 months 75.48 87.71 94.64 307572 1 month 40° C./75% RH 69.13 81.39 87.81 318595 3 months 51.00 61.41 66.26 307579 1 month 60° C. 65.73 75.78 81.76 Morphine-6- 299618 Initial 84.11 89.44 100.71 glucuronide 307569 1 month 25° C./60% RH 81.96 88.23 99.32 fumarate 318590 3 months 81.20 87.15 98.11 307576 1 month 40° C./75% RH 77.62 84.17 94.76 318597 3 months 71.64 79.38 89.37 307583 1 month 60° C. 77.33 82.11 92.44 Morphine-6- 299619 Initial 83.61 88.28 99.40 glucuronide 307568 1 month 25° C./60% RH 80.27 86.66 97.56 Maleate 318591 3 months 80.04 85.11 95.81 307575 1 month 40° C./75% RH 77.07 83.28 93.75 318598 3 months 72.37 78.73 88.63 307582 1 month 60° C. 76.46 80.36 90.47 Morphine-6- 299620 Initial 83.90 89.21 108.12 glucuronide 307567 1 month 25° C./60% RH 84.57 91.37 110.76 phosphate 318592 3 months 84.25 91.16 110.50 307574 1 month 40° C./75% RH 80.20 92.00 111.52 318599 3 months 79.02 92.40 112.01 307581 I month 60° C. 80.69 88.33 107.08 Morphine-6- 299622 Initial 91.07 99.79 99.79 glucuronide 307566 1 month 25° C./60% RH 90.77 99.61 99.61 base 318593 3 months 91.84 100.27 100.27 307573 1 month 40° C./75% RH 89.94 99.45 99.45 318600 3 months 88.67 97.15 97.15 307580 1 month 60° C. 89.31 96.18 96.18

TABLE 4 Related Substances: Example 3 Total Total Known Related Substances (%) Total Un- Related Laboratory Time Storage Mor- Known known Substances Description Reference Point Condition HN75076 phine HN67003 HN33177 HN75083 (%) (%) (%) Morphine-6- 299615 Initial 0.01 ND 0.15 0.69 0.23 1.08 0.64 1.72 glucuronide 307571 1 month 25° C./60% RH ND ND 0.69 0.63 0.27 1.59 2.70 4.29 sulphate 318587 3 months ND 0.17 1.36 0.52 0.53 2.58 6.58 9.16 307578 1 month 40° C./75% RH 0.06 0.21 1.58 0.50 0.74 3.09 6.69 9.78 318594 3 months 0.04 0.37 1.72 0.23 0.58 2.75 15.23 17.98 307585 1 month 60° C. 0.26 0.72 2.73 0.23 0.61 4.55 13.70 18.25 Morphine-6- 299616 Initial ND ND 0.04 0.72 0.10 0.86 0.08 0.94 glucuronide 307570 1 month 25° C./60% RH ND ND ND 0.74 0.03 0.77 0.07 0.84 hydrobromide 318588 3 months ND ND ND 0.77 0.04 0.81 0.12 0.93 307577 1 month 40° C./75% RH 0.01 ND ND 0.74 0.05 0.80 0.00 0.80 318595 3 months 0.02 ND ND 0.70 ND 0.72 0.00 0.72 307584 1 month 60° C. 0.04 ND 0.10 0.66 0.02 0.82 0.38 1.20 Morphine-6- 299617 Initial 0.01 ND 0.07 0.63 0.06 0.77 0.47 1.24 glucuronide 307565 1 month 25° C./60% RH 0.04 ND 0.38 0.63 0.03 1.08 1.33 2.41 hydrochloride 318588 −3 months ND 0.21 1.31 0.50 0.03 2.05 7.47 9.52 307572 1 month 40° C./75% RH 0.34 0.08 3.01 0.41 0.07 3.91 11.25 15.16 318595 3 months 1.67 1.55 3.71 0.07 0.01 7.01 51.57 58.58 307579 1 month 60° C. 0.55 0.46 3.55 0.12 0.03 4.71 16.23 20.94 Morphine-6- 299618 Initial ND ND 0.04 0.77 0.05 0.86 0.09 0.95 glucuronide 307569 1 month 25° C./60% RH ND ND ND 0.80 0.03 0.83 0.08 0.91 fumarate 318590 3 months ND 0.07 0.26 0.75 0.10 1.18 0.72 1.90 307576 1 month 40° C./75% RH 0.03 0.10 0.58 0.70 0.02 1.43 1.17 2.60 318597 3 months 0.40 0.45 1.56 0.57 ND 2.98 6.09 9.07 307583 1 month 60° C. 0.06 0.24 0.97 0.62 0.02 1.91 1.94 3.85 Morphine-6- 299619 Initial ND ND 0.04 0.76 0.05 0.85 0.00 0.85 glucuronide 307568 1 month 25° C./60% RH ND ND 0.17 0.76 0.05 0.98 0.41 1.39 maleate 318591 3 months ND 0.04 0.58 0.52 0.06 1.20 2.35 3.55 307575 1 month 40° C./75% RH 0.03 0.12 0.94 0.65 0.03 1.77 3.03 4.80 318598 3 months 0.40 0.43 1.68 0.50 ND 3.01 6.93 9.94 307582 1 month 60° C. 0.14 0.32 1.20 0.50 0.02 2.18 3.91 6.09 Morphine-6- 299620 Initial ND ND 0.04 0.75 0.07 0.86 0.00 0.86 glucuronide 307567 1 month 25° C./75% RH ND ND 0.04 0.78 0.03 0.85 0.56 1.41 phosphate 318592 3 months 0.03 0.07 0.16 0.78 0.19 1.23 1.08 2.31 307574 1 month 40° C./75% RH ND ND 0.53 0.70 0.14 1.37 2.07 3.44 318599 3 months 0.12 0.32 0.75 0.59 0.06 1.84 4.15 5.99 307582 1 month 60° C. 0.03 0.18 0.90 0.70 0.27 2.08 3.35 5.43 Morphine-6- 299622 Initial ND ND 0.05 0.87 0.06 0.98 0.00 0.98 glucuronide 307566 1 month 25° C./60% RH ND ND ND 0.88 0.05 0.93 0.07 1.00 base 318593 3 months ND ND 0.04 0.86 ND 0.90 0.52 1.42 307573 1 month 40° C./75% RH ND ND 0.05 0.85 0.03 0.93 0.34 1.27 318600 3 months 0.01 0.07 0.23 0.95 ND 1.26 3.08 4.34 307580 1 month 60° C. ND ND 0.19 0.83 0.02 1.04 1.27 2.31 

1. A hydrobromide salt of morphine-6-β-D-glucuronide (M6G.HBr).
 2. A pharmaceutical composition comprising an analgesically effective amount of M6G.HBr and a pharmaceutically acceptable carrier, excipient, or diluent.
 3. A pharmaceutical composition for the treatment of breathlessness in a subject with advanced cancer comprising an effective amount of M6G.HBr and a pharmaceutically acceptable carrier, excipient, or diluent.
 4. M6G.HBr for use as a medicament.
 5. A method of making a a medicament for the treatment of pain, wherein the medicament comprises M6G.HBr.
 6. The method according to claim 5, wherein the pain is moderate to severe in acute or chronic conditions.
 7. A method of making a medicament for the treatment of breathlessness in a subject with advanced cancer, wherein the medicament comprises M6G.HBr.
 8. A method of treating pain in a subject comprising administering the subject with an analgesically effective amount of M6G.HBr.
 9. A method of treating breathlessness in a subject with advanced cancer comprising administering the subject an effective amount of M6G.HBr, wherein the M6G.HBr reduces the breathlessness.
 10. A method of making M6G.HBr comprising the steps of (i) contacting a hydrogen bromide solution with a solution of M6G in methanol; (ii) contacting the solution resulting from step (i) with an organic solution to precipitate M6G.HBr; and (iii) isolating the precipitated M6G.HBr.
 11. The method according to claim 10, wherein the solutions are at −15° C., or below.
 12. The method of claim 10 further comprising an additional step of washing the precipitated M6G.HBr to minimize the amount of organic solution present.
 13. The method according to claim 12, wherein the precipitated M6G.HBr is washed with diethyl ether.
 14. The method according to claim 10, wherein the organic solution used at step (ii) is 2-propanol. 